old petrol

[kujawski]

just a quick question
Does anyone know how long petrol can be kept before it is difficult to start an engine, reason i ask have a boat filled with unleaed aug last year, (used to run no problem), (every thing has been checked by myself) etc when starting takes ages will eventually start but ruff running, will replacement of petrol solve my probelm, because the tank is full and it holds 100 litres (a bit of a waste if i have to replace it )

[Toureman]

It is reccomended that you do not leave petrol in the tank for a year as it "goes off" this usually happens with garden mowers etc. but it should start, perhaps you have sone other problem.

The carb can get bunged up if the petrol is just sitting there for a long period.

[Razzle]

At the bike shop, we usually take out about half of the old petrol and fill up with new. If you keep the petrol in a sealed can, it will last longer but not indefinitely.
The problem you might now face is "varnish" building up in the carb(s). Suggest you run a few sprays of carb cleaner (any motorbike shop will sell it) through the intakes. If you strip the carbs, don't get cleaner on the rubber diaphragm! (If you do, and they go out of shape, an ho8ur in the fridge will sort 'em out.

[Razzle]

add some new petrol, about 50:50 with the old stuff.
That's what we do in the mortorbikes we repair.
Suggest you run some carb cleaner through the intakes when it does start to clear any varnish buildup.

[colin6789]

Petrol sold during the winter has more volatile components to aid starting in cold weather. If it had been left for nearly a year there will be not much volatiles left for starting. You could try adding a starting aid plus redex to clean out any gummed up petrol deposits. could you use a can of new petrol for starting and then add some winter petrol later in the year.

[Melliexr]

A lot will depend on how highly tuned the engine is. My reasonably tuned Husqvarna motorbike really gets the hump if you leave it for more than a couple of weeks. On the other hand, my 36 year old Land Rover had been left for a year and, (with a good battery) started first time.
I'd suggest in future you only keep the tank a quarter full and add in whatever you think you're going to use on each trip so it keeps the fuel relatively fresh.

[eggobako]

believe it or not refinerys like to shift unleaded within a fortnight! after that its past its best if you havesome in a jerrycan it can be rejuvenated by leaving it in the sun in a sealed can this isa short term fix tho and you would be better mixing it in with fresh fuel

[whitt1105]

The octane levels in petrol vastly reduce with age even in a sealed container -like you tank. I suggest you top it up with fresh petrol and if you can get to an air filter use easy start. The redex idea is also a good suggestion but keep it to the dosage stated on the label. My dad thought it would be good to put two bottles in his tank a while ago and the car was glitchy thereafter!!
Davey

[Caladon]

Left for a long period of time, petrol can "go off" as the combustive elements eventually evaporate away and the rest can turn to a very mild acid, although the engine should still run, even if it is rough.
Diesel is different, however (in reference to the chaps 26 year old landy).

To be on the safe side I would drain the lot, disposing of it ecofriendly at a recycling plant, giving the engine a simple service (which should be done on a yearly basis anyway) and refill.